Background Insulin-like signaling (IS) is a conserved pathway in all metazoans. In insects, IS pathway is activated by the binding of Insulin-like peptides (ILPs) and insulin receptor (InR), and is involved in the development, reproduction, and longevity by regulating ERK/AKT cascades. A varying number of ILPs were identified in the Aedes aegypti mosquitos and other insects. Aedes Albopictus (Ae. Albopictus), a major vector for transmitting dengue fever, is fast spreading worldwide. Until now, the molecular and expression characteristics of IS pathway have not been investigated in Ae. Albopictus. Methods The orthologues of ILP in Ae. albopictus genome assembly were analyzed by using sequence blast. Phylogenetic analysis and molecular characterization were performed to identify the functional domains of Ae.albopictus ILPs (AalbILPs). Quantitative analysis was performed to determine the expression characteristics of ILPs, InR and ERK/AKT cascades in the lifespan, and different tissues of female adults after blood feeding. In addition, knockdown of InR was achieved by feeding larvae with E.coli-producing dsRNA to investigate the impact of IS pathway on mosquito development. Results We identified seven putative AalbILP genes in the Ae. Albopictus genome assembly, based on nucleotide similarity to the ILPs of Ae. Aegypti and other insects. Bioinformatics and molecular analyses suggested that the AalbILPs contain the structural motif which is conserved in the insulin superfamily. Expression levels of AalbILPs, InR and ERK/AKT varied among developmental stages and between male and female Ae. Albopictus. Quantitative analyses revealed that expression of ILP6, the putative orthologue of the IGF, was highest in midgut of female adults after blood meals. Knockdown of InR induces a significant decrease in the phosphorylation levels of ERK and AKT proteins, and results in developmental delays and smaller body sizes of Ae. Albopictus mosquito. Conclusions The IS pathway of Ae. Albopictus mosquito contains ILP1-7, InR, and ERK/AKT cascades, which exhibited different developmental and tissue expression characteristics. Feeding larvae with E.coli-producing InR dsRNA blocks the ERK and AKT cascades and interferes with the development of Ae. Albopictus mosquito. Our data suggest that IS pathway plays an important role in the metabolism and developmental process and could represent a target for controlling mosquito-borne diseases.

Background Insulin-like signaling (IS) in insects is a conserved pathway that regulates development, reproduction and longevity. Insulin-like peptides (ILPs) activate the IS pathway by binding to the insulin receptor (InR) and trigger the ERK and AKT cascades. A varying number of ILPs were identified in Aedes aegypti mosquito and other insects. Aedes albopictus is an invasive mosquito which transmits dengue and Zika viruses worldwide. Until now, the molecular and expression characteristics of IS pathway in Ae. albopictus have not been investigated. Methods The orthologues of ILP in Ae. albopictus genome assembly was analyzed by using sequence blast. Phylogenetic analysis and molecular characterization were performed to identify the functional domains of ILPs. Quantitative analysis was performed to determine the expression characteristics of ILPs, InR as well as ERK and AKT in mosquito development and different tissues of female adults after blood-feeding. In addition, the knockdown of InR was achieved by feeding larvae with Escherichia coli-producing dsRNA to investigate the impact of IS pathway on mosquito development. Results We identified seven putative ILP genes in Ae. albopictus genome assembly, based on nucleotide similarity to the ILPs of Ae. aegypti and other insects. Bioinformatics and molecular analyses suggested that the ILPs contain the structural motif which is conserved in the insulin superfamily. Expression levels of ILPs, InR as well as ERK and AKT varied in Ae. albopictus development stages and between male and female adults. Quantitative analyses revealed that expression of ILP6, the putative orthologue of the insulin growth factor peptides, was highest in the midgut of female adults after blood-feeding. Knockdown of Ae. albopictus InR induces a significant decrease in the phosphorylation levels of ERK and AKT proteins and results in developmental delays and smaller body sizes. Conclusions The IS pathway of Ae. albopictus mosquito contains ILP1-7, InR and ERK/AKT cascades, which exhibited different developmental and tissue expression characteristics. Feeding Ae. albopictus larvae with E. coli-producing InR dsRNA blocks the ERK and AKT cascades and interferes with the development of mosquito. Our data suggest that IS pathway plays an important role in the metabolism and developmental process and could represent a potential target for controlling mosquito-borne diseases. Graphical Abstract